1. Field of the Invention
The present invention is directed to multi-sectional linear ionizing bars and other corona discharge based ionization systems, processes and apparatus for charge neutralization. The invention is particularly useful in (but not limited to) Flat Panel Display (FPD) industrial applications. Accordingly, the general objects of the invention are to provide novel systems, methods and apparatus of such character.
2. Description of the Related Art
Conventional static neutralization systems for the FPD industry are usually composed of: (1) a bar type ionization cell having a group of pointed emitters and non-ionizing reference electrode(s); (2) a clean air (gas) supply system having a group of jet type nozzles surrounding each ion emitter and connected to an air channel; and (3) a control system with an AC or pulsed AC high voltage power supply connected to the ionization cell.
Charge neutralization in the FPD industry typically entails neutralization of large charged objects at relatively close distances and at rapid throughput rates. For example, the front and back of glass panels having a length and a width exceeding 3000 mm may need to be charge-neutralized wherein the distance between an ionizing bar(s) and the display panels usually ranges from 50-100 mm up to 1000 mm or more, and wherein the display panels are transported at high speeds using robotics systems.
The use of traditional charge-neutralization ionizing bars of the type described above presents several deficiencies/drawbacks/limitations in trying to satisfy the above-described demanding requirements for charge neutralization of the FPD industry. These deficiencies may include:
The high cost of traditional ionization cells incorporating a multiplicity of emitter points due to the need for (1) several individual connectors between a high voltage power supply and the emitter(s), and (2) a relatively complicated air/gas delivery system;
The high cost of operating and maintaining traditional ionization cells, including the cost of (1) cleaning nozzles and emitter points, and (2) high clean dry air (CDA) or nitrogen gas consumption during operation;
Insufficient cleanliness of the ionized gas stream because the higher quality of high resolution flat panel displays requires low or no particle emission (at least no particles larger than 0.1 micron) from the ion emitter(s);
Unacceptably long discharge times for electrostatic charges because display panel throughput rates demand higher charge neutralization efficiency than has been heretofore available; and
Unacceptably high voltage swings and balance off-sets because lower voltage swings and balance offset voltages are needed to minimize the effects of induced electric fields on processed panels.
Charge neutralizing bars with linear ionizers (ionizing cells comprising long thin wire(s) as emitter(s)/electrode(s)) have been suggested in (1) U.S. Pat. No. 7,339,778, entitled “Corona Discharge Neutralizing Apparatus”; (2) U.S. Pat. No. 8,048,200, entitled “Clean Corona Gas Ionization For Static Charge Neutralization”; and (3) U.S. Patent Application Publication US 2007/0138149. U.S. Pat. No. 7,339,778, entitled Corona Discharge Static Neutralizing Apparatus, and issued on Mar. 4, 2008 is hereby incorporated by reference in its entirety. U.S. Pat. No. 8,048,200, entitled Clean Corona Gas Ionization For Static Charge Neutralization, and issued on Nov. 1, 2011 is also hereby incorporated by reference in its entirety. Further ionizing bars with wire emitters are currently produced by AB Liros Electronic of Malmö, Sweden and/or Liros Electronic of Hamburg, Germany using the following product names: standard series ionizers and/or SER series ionizing tubes.
Common problems encountered by the use of stretched wire emitter ionizers (linear ionizers) can be due to wire sagging and vibration effects. Thus, a long thin wire emitter requires relatively high tension and intermediate wire supports. In addition, high velocity air streams directly blowing ions off of the linear wire emitters exacerbate the inherent problem of wire vibration and accelerate contamination of the wire emitter (as a result of particles attracted to the wire from entrained ambient air). Both factors make wire emitters prone to breakage and complicate linear ionizer bar maintenance.